on 5/14/09 7:58 PM, Mark Sapiro said:
Normally, I would defer to you for all things MTA as your knowledge and experience in this area are far greater than mine, but I have been under the impression that if an MTA has two or more messages to deliver to the the same remote MX, that it can and perhaps will deliver them in one SMTP session as follows
My understanding is that the issue here isn't so much the single SMTP connection, which may or may not get re-used, depending on the queueing strategy of the sender.
If you want to increase your efficiency in this area, then you make sure that your submission actually just puts the message into the queue in deferred mode and doesn't make an immediate delivery attempt, and of course you turn off all spam and other access control checks on the outbound side, since you should have already done all those on inbound. You then allow later queue runs to come along and pick that up, along with any other messages bound for that destination.
I think we cover this in the various "performance" articles in the FAQ Wiki.
My understanding is that the issue here is whether or not the VERP'ed format will be understood and usable by Mailman if there is a bounce, and how many unique messages will be delivered, as opposed to how many connections will be created to deliver the messages.